1. Field of the Invention
The present invention relates to an idle control device for fuel cell vehicles, and in particular, relates to a control device and a control method for controlling the idle stop of fuel cell vehicles, in which a hybrid type power source device provided with a power storage unit assists the power supply of the fuel cell to the load.
2. Description of the Related Art
As disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 8-214453, a conventional-type fuel cell vehicles are known, in which a solid polymer membrane-type fuel cell is installed and this type of fuel cell vehicles is provided with a hybrid-type power source which comprises a power storing device such as a battery or a capacitor in addition to the fuel cell in order to improve an output response of the fuel cell caused by the supply of hydrogen as the fuel or supply of air as an oxidizing agent.
In the above-described conventionally known fuel cell vehicles, as shown in the power generation efficiency shown in FIG. 6, the power consumption of the auxiliary devices for driving the fuel cell, such as the air compressor, is relatively low when the fuel cell generates intermediate or higher outputs, and in such intermediate or high output regions of the fuel cell, the fuel consumption rate for a unit amount of power generation increases in proportion to the output of the fuel cell.
In contrast, in the low output region of the fuel cell, the power consumption rate of the auxiliary devices becomes relatively high, and the power generation efficiency of the fuel cell decreases. Therefore, at the time of idle driving such that the power consumption for driving the vehicle is zero, if the power is supplied from the fuel cell, a problem arises in that the fuel consumption efficiency of the vehicle is deteriorated.
The present invention is made in order to solve the above-described problems, and the present invention provides an idle control apparatus for a fuel cell vehicle, which is provided with a hybrid-type power source device, and which is capable of improving the fuel efficiency.
A first aspect of the present invention provides an idle control device for a fuel cell vehicle, comprising a power storage unit (for example, the power storage unit 12 described later in the present embodiment) for supplying electric power to a driving motor (for example, a driving motor 13 described later in the present embodiment) of the fuel cell vehicle and/or auxiliary devices of the fuel cell vehicle for assisting the output of the fuel cell, and for storing energy generated by the fuel cell (for example, a fuel cell 11 described later in the present embodiment) and regenerative energy to be obtained by a regenerative operation of the driving motor; and a fuel cell driving device (for example, an air compressor 15 described later in the present embodiment) for supplying reaction gases (for example, hydrogen gas and air described later in the present embodiment) for power generating and a fuel cell drive control device (for example, ECU 18 described later in the present embodiment) for controlling operation of the fuel cell driving device; wherein the fuel cell driving device stops the power generation of said fuel cell by stopping supply of said reaction gases when the fuel cell vehicle is in a predetermined idling state.
According to the idle control device for the fuel cell vehicle of the present invention, in response to driving conditions, the power generation of the fuel cell is stopped by stopping the fuel cell driving auxiliary devices such as an air compressor, so that it is possible to improve the fuel consumption efficiency of the present fuel cell vehicle.
In the above idle control device for a fuel cell vehicle comprising a rotational rate detecting device (for example, a magnetic pole position-angular velocity detector 35 described later in the present embodiment) for detecting a rotational rate of the driving motor, a brake operation state detecting device (for example, a brake operation state detecting device BR described later in the present embodiment) for detecting the operational state of a brake of the fuel cell vehicle, a state of charge detecting device (for example, a terminal voltage VSt of the power storage unit described later in the present embodiment) for detecting a state of charge of said power storage unit, and a load detecting device (for example, a control portion 23 of PDU 14 and the air compressor 15 described later in the present embodiment) for detecting an electric load of the fuel cell vehicle, the power generation of the fuel cell vehicle is stopped by stopping supply of said reaction gases, when said rotational rate detecting device, said brake operation state detecting device, said state of charge detecting device, and said load detecting device detect that the fuel cell vehicle is in the idling state which is capable of stopping the power generation of the fuel cell by stopping supply of the reaction gases.
The above idle control device for the fuel cell vehicle with the above constitution makes it possible not only to improve the fuel consumption efficiency, but also to restart the fuel cell by driving the fuel cell drive auxiliary devices such as the air compressor.
In the above idle control device for a fuel cell vehicle, when the rotational rate is zero or is lower than a predetermined rotational rate, the brake is in the ON state, the state of charge is less than a predetermined state of charge, and the electric load is less than a predetermined load, it is determined that the vehicle is in the idling state capable of stopping the power generation of the fuel cell and the power generation of the fuel cell is stopped by stopping supply of the reaction gases by the fuel cell driving device.
According to the above idle control device for the fuel cell vehicle, in determining to execute the idle stop, it is determined whether the state of charge of the power storage unit is higher than a predetermined value, so that it is possible to ensure the electric power for restarting the fuel cell and the fuel cell can be restarted smoothly.
In the above idle control device for a fuel cell vehicle, when the fuel cell driving device is stopping, the fuel cell drive control device actuates the fuel cell driving device when the state of charge of the power storage unit is reduced below a predetermined state of charge.
According to the above constitution of the idle control device, when the fuel cell is restarted while the fuel cell is stopping, electric power is first supplied from the power storage unit to the fuel cell drive auxiliary device such as the air compressor, and power generation by the fuel cell is restarted so that the power supply from the power storage unit is reduced. Thus, charging and discharging of the power storage unit is repeated depending on the driving conditions of the fuel cell vehicle, and when the fuel cell vehicle stops, the power storage unit is charged by the regenerative operation and the terminal voltage increases.
Note that when a capacitor is used as the power storage unit, the terminal voltages of the capacitor are set in place of the state of charge of the capacitor such that the power generation of the fuel cell is stopped when the terminal voltage exceeds a predetermined upper limit (for example, around 360V), and the power generation of the fuel cell is restarted when the terminal voltage of the fuel cell is reduced below the lower limit (for example, around 300V).
When a battery is used as the power storage unit, the state of charge of the battery is set such that the fuel cell is stopped when the state of charge of the battery exceeds a predetermined upper limit of 81% and the fuel cell is restarted when the state of charge of the battery is reduced below a predetermined lower limit of 56%.
Thereby, even when the fuel cell is stopping, it is possible to restart the fuel cell drive auxiliary device such as the air compressor, and the fuel consumption efficiency can be improved.
In the above idle control device for the fuel cell vehicle, the predetermined state of charge is set to a value capable of driving the fuel cell driving device and the driving motor for a predetermined time.
According to the above idle control device for a fuel cell vehicle, the predetermined state of charge for stopping the power generation of the fuel cell is set to a value of a state of charge which is capable of supplying power to the fuel cell drive auxiliary device such as the air compressor for a predetermined time, for example, an hour. Accordingly, even while the fuel cell is stopping, the driving motor and the air compressor can be restarted smoothly.